1. Field of the Invention
The invention relates to an oil pan structure.
2. Description of the Related Art
Usually, an oil pan is provided below the cylinder-block of an internal combustion engine used in, for example, a vehicle. This oil is used, for example, to cool, and lubricate the internal combustion engine. Such an oil pan is provided with a tubular level-gauge guide where one end opens into the reservoir portion of the oil pan, in which oil is stored. Generally, an oil level-gauge inserted in this level-gauge guide measures the amount of oil stored in the reservoir portion.
When the oil in oil pan needs to be replaced with new oil, an oil changer, instead of the oil level-gauge, may be inserted into the level-gauge guide to draw the used oil up from the reservoir portion. Ideally, very little or no residual amount of the used oil remains in the reservoir portion after removal of the used oil.
However, because it is difficult to accurately determine whether the end of the oil changer is guided to the deepest portion of the reservoir portion when the oil changer draws up the oil in the reservoir portion, the following problem may arise. If the end of the oil changer is not guided to the deepest portion, some oil remains in the deepest portion even after draw-up of the used oil ends, because the oil changer cannot efficiently draw up the oil in the reservoir portion.
The following approach to address such a problem is known, for example, as described in Japanese Patent Application Publication No. JP-A-2002-221017. A cylindrical body, which connects the lower end of the level-gauge guide to the bottom surface of the oil pan, is arranged in the reservoir portion of the oil pan. As a result, a gas-tight seal is formed between the lower end of the level-gauge guide and the bottom surface of the oil pan. In addition, a passage-forming member is attached to the bottom surface of the oil pan. This passage-forming member forms a passage that connects the bottom surface of the oil pan, which contacts the lower end of the cylindrical body, to the deepest portion of the reservoir portion. Then, two through-holes are formed. One through-hole provides communication between the space in the cylindrical body and the passage formed by the passage-forming member. The other through-hole provides communication between the passage and the deepest portion of the reservoir portion. With these two through-holes, the oil can flow between the level-gauge guide and the deepest portion of the reservoir portion. Thus, the oil changer inserted in the level-gauge guide can smoothly draw the oil up from the deepest portion of the reservoir portion through the passage formed by the passage-forming member and the cylindrical body.
According to the described approach, however, additional components are required. For example, the cylindrical body needs to be arranged in the oil pan, and the passage-forming member needs to be attached to the bottom surface of the oil pan. This increases the number of components, and, therefore, complicates the arrangement of components. In addition, because the through-holes are required to form the passage through which the oil changer draws up the oil, the structure of the oil pan becomes considerably complicated.